As for the killing specifically. My brother made a silly joke to me the other day when I brought this up with him.

Ironman traps Killian in his suit and blows him to hell, that doesn't work so they try a few more things and eventually smoke him and badly. Then his hot half naked middle aged girl friend and himself make out and we get fire works and everyone cheers, cut to the disney logo of all things.

Superman, faces an enemy that will wipe the planet out in less than 24 hours after superman isn't able to fight any more. And unlike the marvel u, there is no one else to take up the fight. He's put into a corner, makes a tough choice, smokes his enemy, shows a very vivid amount of regret, his hot middle aged overly dressed girl friend shows up to console him, tears are shed...

And people say superman is not being held to a higher standard then the rest?
His two cents.